Method and System for Operating Multi-Subscriber Identity Module (sim) Mobile Device in Wireless Communication Networks

1. A method for operating a multi-subscriber identity module (SIM) mobile device, the method comprising: identifying an equivalent PLMN (EPLMN) cell as a common suitable public land mobile network (PLMN) cell between a first radio frequency (RF) unit and a second RF unit of said mobile device, wherein said first RF unit and said second RF unit of said mobile device are currently camped on different PLMN cells corresponding to different public land mobile networks (PLMNs) and said different PLMN cells comprises an equivalent PLMN (EPLMN) cell and a home PLMN (HPLMN) cell each corresponding to said first RF unit and said second RF unit respectively; enforcing at least one of said first RF unit and said second RF unit to camp on said common suitable PLMN cell, even though said at least one of said first RF unit and said second RF unit is capable of camping on the HPLMN; and disabling one of said first RF unit and said second RF unit when at least one of said first RF unit and said second RF unit camps on said common suitable PLMN cell.

2. The method of claim 1 , wherein said method further comprises receiving broadcast and paging information on at least one of said first RF unit and said second RF unit from said camped common suitable PLMN cell.

3. The method of claim 1 , wherein said different PLMN cells corresponding to said different public land mobile networks (PLMNs) corresponds to a best suitable PLMN cell associated with said first RF unit and said second RF unit.

4. The method of claim 1 , wherein said method further comprises: holding each of a high priority PLMN (HPPLMN) search timer associated with each of said first RF unit and said second RF unit in an inactive mode when at least one of said first RF unit and said second RF unit are camped on said EPLMN cell.

5. The method of claim 4 , wherein said method further comprises: initiating each of said HPPLMN timer associated with each of said first RF unit and said second RF unit when said first RF unit and said second RF unit are camped on said different PLMN cells and when said common suitable PLMN cell is unavailable between said first RF unit and said second RF unit.

6. The method of claim 1 , wherein identifying said common suitable PLMN cell between said first RF unit and said second RF unit of said mobile device comprises: detecting an event at said mobile device; determining whether a predefined condition is satisfied upon detecting the event at said mobile device; selecting at least one of said first RF unit and said second RF unit to perform a PLMN search based on at least one state of said first RF unit and state of said second RF unit in response to determining that said predefined condition is satisfied upon detecting the event at said mobile device; obtaining a list of cell information from the selected at least one of said first RF unit and said second RF unit, wherein said list of cell information corresponds to said first RF unit and said second RF unit; creating a temporary list of PLMN cells corresponding to said first RF unit and said second RF unit based on said list of cell information; and storing said temporary list in said mobile device.

7. The method of claim 6 , wherein said cell information comprises at least one of said available PLMN cell, available PLMN cell in stored cell selection information corresponding to at least one of said first RF unit and said second RF unit, cells of corresponding PLMNs, measurement information required for ranking PLMN cells, PLMN Identifiers (IDs) of said PLMN cells, neighbor cell information, and measurement information of camped PLMN cell.

8. The method of claim 6 , wherein said method further comprises: determining whether said temporary list comprises of said HPLMN cell of said first RF unit and said second RF unit and said neighbor cell information of said HPLMN cell of said first RF unit and said second RF unit; requesting at least one of said first RF unit and said second RF unit to update said neighbor cell information of said HPLMN cell and said measurement information of corresponding neighbor cells for ranking along with said PLMN IDs of corresponding said neighbor cells; and updating said neighbor cell information of said HPLMN cell and said measurement information of corresponding said neighbor cells for ranking along with said PLMN IDs of corresponding said neighbor cells in said temporary list.

9. The method of claim 6 , wherein said predefined condition comprises one of: determining whether at least one said common EPLMN cell is available between said first RF unit and said second RF unit; and determining whether said HPLMN cell associated with one of said RF unit and said second RF unit is available in an EPLMN list of other one of said first RF unit and said second RF unit.

10. The method of claim 6 , wherein determining whether said predefined condition is satisfied upon detecting the event at said mobile device comprises: determining whether said first RF unit and said second RF unit are camped on said different PLMN cells; initiating a common suitable PLMN search timer in response to determining that said first RF unit and said second RF unit are camped on said different PLMN cells; and requesting said first RF unit and said second RF unit to provide said neighbor cell information of corresponding registered PLMN (RPLMN) cell along with said measurement information required for ranking the cells and corresponding said PLMN ids of said PLMN cells upon expiry of said common suitable PLMN search timer; and storing said neighbor cell information of corresponding Registered PLMN (RPLMN) cell along with said cell information in said temporary list.

11. The method of claim 10 , wherein determining whether said first RF unit and said second RF unit are camped on said different PLMN cells comprises: terminating said common suitable PLMN search timer in response to determining that said first RF unit and said second RF unit are camped on said common suitable PLMN cell.

12. The method of claim 6 , wherein said method further comprises: receiving an update message from at least one of said first RF unit and said second RF unit, wherein the update message comprises of an updated cell information associated with at least one of said first RF unit and said second RF unit; and updating said temporary list based on received said update message.

13. The method of claim 6 , wherein said event comprises one of: powering on said mobile device and searching for one of respective HPLMN cell and said RPLMN cell or said first RF unit and said second RF unit triggers said PLMN search to recover from loss of coverage; triggering said PLMN search for one of said respective HPLMN cell and said RPLMN cell by one of said first RF unit and said second RF unit, wherein one of said first RF unit and said second RF is in service; triggering a blind search by said first RF unit and said second RF unit; performing a reselection by said first RF unit and said second RF unit, wherein said first RF unit and said second RF unit are camped on said different PLMN cells; and performing said reselection when one of said first RF unit and said second RF unit is disabled, as both said first RF unit and said second RF unit are listening to same PLMN cell.

14. The method of claim 13 , wherein said method further comprises: detecting said event of powering on said mobile device and searching for one of said respective HPLMN cell and said RPLMN cell or said first RF unit and said second RF unit triggers said PLMN Search to recover from loss of coverage; requesting one of said first RF unit and said second RF unit to perform said PLMN search for list of said PLMN cells available in said stored cell selection information of said first RF unit and second RF unit and to provide said measurement information of each said PLMN cells along with said cell information upon detecting said event; receiving said measurement information of each said PLMN cells and said cell information from requested one of said first RF unit and said second RF unit; and creating said temporary list of PLMN cells and storing said measurement information of each said PLMN cells and said PLMN IDs of the corresponding said PLMN cells in said temporary list.

15. The method of claim 13 , wherein said method further comprises: detecting said event of triggering said PLMN search for one of said respective HPLMN cell and said RPLMN cell by one of said first RF unit and said second RF unit at said mobile device, wherein one of said first RF unit and said second RF is in service; requesting one of said first RF unit and said second RF which is in service to perform said PLMN search for said list of PLMN cells which are available in said stored cell selection information for RF unit which is recovering from loss of coverage along with said cell information and said neighbor cell information of said camped PLMN cell of said RF unit which is in service from broadcasted system information upon detecting said event; receiving said list of PLMN cells which are available in said stored cell selection information for said RF unit which is recovering from loss of coverage along with said cell information and said neighbor cell information of said camped PLMN cell of said RF unit which is in service from requested one of said first RF unit and said second RF which is in service; storing said list of PLMN cells which are available in said stored cell selection information for said RF unit which is recovering from loss of coverage along with said cell information and said neighbor cell information of said camped PLMN cell of said RF unit which is in service, in said temporary list; and updating said temporary list with said list of PLMN cells which are available in said stored cell selection information for said RF unit which is recovering from loss of coverage along with said cell information and said neighbor cell information of said camped PLMN cell.

16. The method of claim 13 , wherein said method further comprises: detecting said event of performing said reselection by said first RF unit and said second RF unit at said mobile device, wherein said first RF unit and said second RF unit are camped on said different PLMN cells; requesting said first RF unit and said second RF unit to provide said measurement information, said cell information and said neighbor cell information of camped RPLMN cell corresponding to said first RF unit and said second RF unit upon detecting said event; and storing said measurement information, said cell information and said neighbor cell information of said camped RPLMN cell corresponding to said first RF unit and said second RF unit in said temporary list.

17. The method of claim 13 , wherein said method further comprises: detecting said event of performing said reselection when said first RF unit is active and is camped on said common suitable PLMN cell and when said second RF unit is disabled at said mobile device; determining whether camped cell measurements of said first RF unit which is active satisfies a custom defined S (CS) criteria; monitoring camped cell signal condition without performing reselection for said first RF unit which is active in response to determining that said camped cell measurements of said first RF unit which is active satisfies said CS criteria; updating in said mobile device with said camped PLMN cell of said first RF unit which is active as unsatisfying said CS criteria in response to determining that said CS criteria is unsatisfied by said camped cell measurements of said first RF unit which is active; and updating and storing said neighbor cell information of said camped PLMN cell along with said measurement information required for ranking said PLMN cells and said PLMN ids of said neighbor cells in said temporary list.

18. A multi-subscriber identity module (SIM) mobile device, the mobile device comprising: a processor configured to: identify an equivalent PLMN (EPLMN) cell as a common suitable public land mobile network (PLMN) cell between a first radio frequency (RF) unit and a second RF unit of said mobile device, wherein said first RF unit and said second RF unit of said mobile device are currently camped on different PLMN cells corresponding to different public land mobile networks (PLMNs) and said different PLMN cells comprises an equivalent PLMN (EPLMN) cell and a home PLMN (HPLMN) cell each corresponding to said first RF unit and said second RF unit respectively; enforce at least one of said first RF unit and said second RF unit to camp on said common suitable PLMN cell, even though said at least one of said first RF unit and said second RF unit is capable of camping on the HPLMN; and disable one of said first RF unit and said second RF unit when at least one of said first RF unit and said second RF unit camps on said common suitable PLMN cell.

19. The device of claim 18 , wherein said device further comprises: a radio frequency (RF) unit configured to receive broadcast and paging information on at least one of said first RF unit and said second RF unit from said camped common suitable PLMN cell.

20. The device of claim 18 , wherein said different PLMN cells corresponding to said different public land mobile networks (PLMNs) corresponds to a best suitable PLMN cell associated with said first RF unit and said second RF unit.

21. The device of claim 18 , wherein said processor is further configured to hold each of said high priority PLMN (HPPLMN) search timer associated with each of said first RF unit and said second RF unit in an inactive mode when at least one of said first RF unit and said second RF unit are camped on said EPLMN cell.

22. The device of claim 21 , wherein said processor is further configured to: initiate each of said HPPLMN timer associated with each of said first RF unit and said second RF unit when said first RF unit and said second RF unit are camped on said different PLMN cells and when said common suitable PLMN cell is unavailable between said first RF unit and said second RF unit.

23. The device of claim 22 , wherein in determining whether said predefined condition is satisfied upon detecting the event at said mobile device, said processor is further configured to: determine whether said first RF unit and said second RF unit are camped on said different PLMN cells; initiate a common suitable PLMN search timer in response to determining that said first RF unit and said second RF unit are camped on said different PLMN cells; and request said first RF unit and said second RF unit to provide said neighbor cell information of corresponding registered PLMN (RPLMN) cell along with said measurement information required for ranking the cells and corresponding said PLMN ids of said PLMN cells upon expiry of said common suitable PLMN search timer; and store said neighbor cell information of corresponding Registered PLMN (RPLMN) cell along with said cell information in said temporary list.

24. The device of claim 23 , wherein in determining whether said first RF unit and said second RF unit are camped on said different PLMN cells, said processor is further configured to: terminate said common suitable PLMN search timer in response to determining that said first RF unit and said second RF unit are camped on said common suitable PLMN cell.

25. The device of claim 18 , wherein in identifying said common suitable PLMN cell between said first RF unit and said second RF unit of said mobile device, said processor is further configured to: detect an event at said mobile device; determine whether a predefined condition is satisfied upon detecting the event at said mobile device; select at least one of said first RF unit and said second RF unit to perform a PLMN search based on at least one state of said first RF unit and state of said second RF unit in response to determining that said predefined condition is satisfied upon detecting the event at said mobile device; obtain a list of cell information from the selected at least one of said first RF unit and said second RF unit, wherein said list of cell information corresponds to said first RF unit and said second RF unit; create a temporary list of PLMN cells corresponding to said first RF unit and said second RF unit based on said list of cell information; and store said temporary list in said mobile device.

26. The device of claim 25 , wherein said cell information comprises at least one of said available PLMN cell, available PLMN cell in stored cell selection information corresponding to at least one of said first RF unit and said second RF unit, cells of corresponding PLMNs, measurement information required for ranking PLMN cells, PLMN Identifiers (IDs) of said PLMN cells, neighbor cell information, and measurement information of camped PLMN cell.

27. The device of claim 25 , wherein said processor is further configured to: determine whether said temporary list comprises of said HPLMN cell of said first RF unit and said second RF unit and said neighbor cell information of said HPLMN cell of said first RF unit and said second RF unit; request at least one of said first RF unit and said second RF unit to update said neighbor cell information of said HPLMN cell and said measurement information of corresponding neighbor cells for ranking along with said PLMN IDs of corresponding said neighbor cells; and update said neighbor cell information of said HPLMN cell and said measurement information of corresponding said neighbor cells for ranking along with said PLMN IDs of corresponding said neighbor cells in said temporary list.

28. The device of claim 25 , wherein said predefined condition comprises one of: determining whether at least one said common EPLMN cell is available between said first RF unit and said second RF unit; and determining whether said HPLMN cell associated with one of said RF unit and said second RF unit is available in an EPLMN list of other one of said first RF unit and said second RF unit.

29. The device of claim 25 , wherein said processor is further configured to: receive an update message from at least one of said first RF unit and said second RF unit, wherein the update message comprises of an updated cell information associated with at least one of said first RF unit and said second RF unit; and update said temporary list based on received said update message.

30. The device of claim 25 , wherein said event comprises one of: powering on said mobile device and searching for one of respective HPLMN cell and said RPLMN cell or said first RF unit and said second RF unit triggers said PLMN search to recover from loss of coverage; triggering said PLMN search for one of said respective HPLMN cell and said RPLMN cell by one of said first RF unit and said second RF unit, wherein one of said first RF unit and said second RF is in service; triggering a blind search by said first RF unit and said second RF unit; performing a reselection by said first RF unit and said second RF unit, wherein said first RF unit and said second RF unit are camped on said different PLMN cells; and performing said reselection when one of said first RF unit and said second RF unit is disabled as said first RF unit and said second RF unit are listening to same PLMN cell.

31. The device of claim 30 , wherein said processor is further configured to: detect said event of powering on said mobile device and searching for one of said respective HPLMN cell and said RPLMN cell or both said first RF unit and said second RF unit triggers said PLMN Search to recover from loss of coverage; request one of said first RF unit and said second RF unit to perform said PLMN search for list of said PLMN cells available in said stored cell selection information of said first RF unit and second RF unit and to provide said measurement information of each said PLMN cells along with said cell information upon detecting said event; receive said measurement information of each said PLMN cells and said cell information from requested one of said first RF unit and said second RF unit; and create said temporary list of PLMN cells and storing said measurement information of each said PLMN cells and said PLMN IDs of the corresponding said PLMN cells in said temporary list.

32. The device of claim 30 , wherein said processor is further configured to: detect said event of triggering said PLMN search for one of said respective HPLMN cell and said RPLMN cell by one of said first RF unit and said second RF unit at said mobile device, wherein one of said first RF unit and said second RF is in service; request one of said first RF unit and said second RF which is in service to perform said PLMN search for said list of PLMN cells which are available in said stored cell selection information for RF unit which is recovering from loss of coverage along with said cell information and said neighbor cell information of said camped PLMN cell of said RF unit which is in service from broadcasted system information upon detecting said event; receive said list of PLMN cells which are available in said stored cell selection information for said RF unit which is recovering from loss of coverage along with said cell information and said neighbor cell information of said camped PLMN cell of said RF unit which is in service from requested one of said first RF unit and said second RF which is in service; store said list of PLMN cells which are available in said stored cell selection information for said RF unit which is recovering from loss of coverage along with said cell information and said neighbor cell information of said camped PLMN cell of said RF unit which is in service, in said temporary list; and update said temporary list with said list of PLMN cells which are available in said stored cell selection information for said RF unit which is recovering from loss of coverage along with said cell information and said neighbor cell information of said camped PLMN cell.

33. The device of claim 30 , wherein said processor is further configured to: detect said event of performing said reselection by said first RF unit and said second RF unit at said mobile device, wherein said first RF unit and said second RF unit are camped on said different PLMN cells; request said first RF unit and said second RF unit to provide said measurement information, said cell information and said neighbor cell information of camped RPLMN cell corresponding to said first RF unit and said second RF unit upon detecting said event; and store said measurement information, said cell information and said neighbor cell information of said camped RPLMN cell corresponding to said first RF unit and said second RF unit in said temporary list.

34. The device of claim 30 , wherein said processor is further configured to: detect said event of performing said reselection when said first RF unit is active and is camped on said common suitable PLMN cell and when said second RF unit is disabled at said mobile device; determine whether camped cell measurements of said first RF unit which is active satisfies a custom defined S (CS) criteria; monitor camped cell signal condition without performing reselection for said first RF unit which is active in response to determining that said camped cell measurements of said first RF unit which is active satisfies said CS criteria; update in said mobile device with said camped PLMN cell of said first RF unit which is active as unsatisfying said CS criteria in response to determining that said CS criteria is unsatisfied by said camped cell measurements of said first RF unit which is active; and update and storing said neighbor cell information of said camped PLMN cell along with said measurement information required for ranking said PLMN cells and said PLMN ids of said neighbor cells in said temporary list.

35. The device of claim 18 , wherein in enforcing at least one of said first RF unit and said second RF unit to camp on said common suitable PLMN cell, said processor is further configured to: determine whether said best ranked PLMN cell for said first RF unit and said second RF unit are same; and enforce at least one of said first RF unit and said second RF unit to camp on said best ranked PLMN cell in response to determining that said best ranked PLMN cell for said first RF unit and said second RF unit are same.

36. The device of claim 35 , wherein said processor is further configured to: determine whether said respective HPLMN cell of said first RF unit and said second RF unit is available in said first list of PLMN cells and said second list of PLMN cells in response to determining that said best ranked PLMN cell for said first RF unit and said second RF unit are different; compute a combined RF unit cell rank for said best ranked PLMN cell of said first RF unit and said best ranked PLMN cell of said second RF unit in response to determining that said respective HPLMN cell of said first RF unit and said second RF unit is available in said first list of PLMN cells and said second list of PLMN cells; and enforce at least one of said first RF unit and said second RF unit to camp on one of said best ranked PLMN cell of said first RF unit and said second RF unit based on said combined RF unit cell rank.

37. The device of claim 36 , wherein in determining whether said respective HPLMN cell of one of said first RF unit and said second RF unit is available in said first list of PLMN cells and said second list of PLMN cells, said processor is further configured to: determine whether one of said respective HPLMN cell associated with one of said first RF unit and said second RF unit is available in said first list of PLMN cells and said second list of PLMN cells; and enforce at least one of said first RF unit and said second RF unit to camp on one of said respective HPLMN cell which is available in said first list of PLMN cells and said second list of PLMN cells.

38. The device of claim 37 , wherein said processor is further configured to: determine whether at least one said common EPLMN cell is available in said first list of PLMN cells and said second list of PLMN cells in response to determining that one of said respective HPLMN cell associated with one of said first RF unit and said second RF unit is unavailable in said first list of PLMN cells and said second list of PLMN cells; and enforce at least one of said first RF unit and said second RF unit to camp on at least one said common EPLMN cell in response to determining that at least one said common EPLMN cell is available in said first list of PLMN cells and said second list of PLMN cells.

39. The device of claim 38 , wherein said processor is further configured to: add rank of said first list of PLMN cells to rank of said second list of PLMN cells for each of said common EPLMN cell in response to determining that more than one common EPLMN cells are available in said first list of PLMN cells and said second list of PLMN cells; and enforce at least one of said first RF unit and said second RF unit to camp on said common EPLMN cell based on the added rank.